The present invention provides an imaging device and a focusing control method capable of enhancing accuracy of a focusing control regardless of subjects even when levels of detection signals of phase difference detection pixels are low. A phase difference AF processing unit (19) generates a defocus amount (Df1) from a result of a correlation operation performed with respect to detection signals obtained by adding up detection signals of plural phase difference detection pixels (52A, 52B) in a pair line (PL1) present in a selected AF area (53) and detection signals of phase difference detection pixels (52A, 52B) in pair lines (PL2, PL3) present in a selected direction among plural directions which are crossing directions crossing an X direction with respect to each of the plural phase difference detection pixels (52A, 52B) in the pair line (PL1). A system control unit (11) performs a focusing control based on the defocus amount (Df1).